A firefighter has been charged with aggravated manslaughter in connection with the death of his 23-month-old son who was left in a pick-up truck for eight hours.

Troy Whitaker, 41, of Palm Harbour, Florida, placed his son Lawson and five-year-old daughter in his pick-up truck on Friday morning and took the girl to school, said the Pinellas County Sheriff's Office.

Whitaker then drove home without taking Lawson to day care and left him unattended inside the truck until about 3.30pm, when he drove to a nearby grocery store.

He did not notice Lawson was still in the back seat of the truck until an hour later when he got home and began unloading groceries, detectives said.